Piston expander for t-slotted and unslotted piston skirts



Aug. 15,1944. G J, W REL 2,355,937

PISTON EXPANDER FOR T-SLOTTED AND UNSLOTTED PISTON SKIRTS;

Filed Nov. 28, 1940 l/v wswro/f; GAE/V J vim/7,54. 57/705 flrfwiwni Patented Aug. 15, 1944 PISTON EXPANDER FOR T-SLOTTED AND UNSLOTTED PISTON SKIRTS Glen J. VVorel, Minneapolis, Minn, assignor to Thexton Manufacturing Company,

Minneapolis, Minn, a corporation of Minnesota Application November 28, 1940, Serial No. 367,510

(01. see-12 5 Claims.

This invention relates to expanders for piston skirts of internal combustion engines and the like, and is an improvement in certain respects on the invention disclosed in my co-pending application entitled Piston expanderfor slotted and unslotted piston skirts, Serial Number 356,608, filed September 13, 1940. The present invention isparticularly adapted for pistons having a T- shaped slot in the skirt thereof as well as for unslotted pistons. The wear on cylinder walls and the skirts of pistons, particularly in internal combustion engines and other engines or analogous devices utilizing connecting rods connected with a crank, causes piston slap with the resultant tilting of the piston which quickly wears the edges of the oil rings so that oil will pump. past the rings causing substantial loss of efficiency in the performance of the engine.

It is an object of my invention to provide an improved and extremely simple expander which resiliently exerts an expansive action on portions of a piston skirt intermediate of the bosses and in a direction transverse to the axis of the piston wrist pin, thereby resiliently taking up for normal Wear and. eliminating the necessity for reboring of cylinders and replacement of pistons.

More specifically, it is an object to provide a piston skirt expander of the class described which utilizes the bosses for the wrist pin as its base of resistance or thrust, and which exerts outward pressure against the inner wall of the piston skirt and along two parallel zones or portions which may be disposed on opposite sides of the slot of a piston having a longitudinal slot and which, likewise, is effective in expanding a considerable Sector of an unslotted piston to compensate for wear.

Still more specifically, it is an object of'the present invention to provide a preferably integral leaf sprin member of some considerable width interposed between the wrist pin bosse and the inner wall of the piston skirt and having a pair of spaced, outwardly extending, pressure applying surfaces or flutings bridged by the integral construction of the member and adapted to exert pressure on the skirt at both sides of and adjacent to a longitudinal slot in the skirt, such as a relatively short, longitudinal slot forming the stem portion of a T-slot.

The structure disclosed in my co-pending application identified herein is highly satisfactory for unslotted pistons, but if utilized on pistonsof the type illustrated herein having a T-slot formed in the upper portion of the skirt, usually causes the expansion or protrusion of one of the edges defining the slot while not afiecting the opposite slot-defining edge, thereby leaving a protruding edge which in the reciprocation of the piston causes damage to the cylinder wall.

With the improved construction disclosed herein, piston skirts of the T-slot type as well as unslotted pistons may be effectively expanded to properly compensate for wear, to eliminate piston slapping and resulting. oil pumping when used with good piston rings.

My improved invention further is adapted for application to longitudinal slotted piston skirts having longitudinal reenforcing ribs at the edges defining the slot to permit such ribs to be spanned and pressure applied at opposite sides of the skirt and along surfaces contingent to the ribbed or reenforced portions.

These and other objects and advantages of my invention will be more fully set forth in the following description made in connection with the accompanying drawing, in which like reference characters refer to the same parts throughout the several views, and in which:

Fig. 1 is a side elevation of a piston of conventional type provided with a T-slot, the outline of an embodiment of my expander being indicated in dotted lines as operatively applied to the interior of the piston skirt construction;

Fig. 2 is a cross section taken on the line 2-2 of Fig. 1;

Fig. 3 is a longitudinal vertical section with the application of a pair of special pliers for attaching or detaching the expander indicated in dotted lines, and

Fig, 4 is a front elevation of my improved piston skirt expander detached.

In the drawing a piston of the type having a T-slo-t through the peripheral wall thereof is illustrated. This T-slot, as is the usual practice, is formed by a circumferential, relatively wide slot T formed in the lower ring groove of the piston head and. a narrower vertical slot S extending from. a point some distance above the lower edge of the skirt to slot T and communicating therewith. A piston head 5 is provided with the usual piston ring grooves 5a and lands 5b which sepa rate the grooves. The head 5 is constructed of greater thickness than the depending piston skirt 6. inaccordance with the usual construction. The skirt. 6 in this conventional piston is continuous with the head and comparatively resilient and flexible, and, asshown, is provided with reenforcin ribs 1 usually cast or integrally constructed with the rest of the piston and defining with the thickness of the skirt proper the vertical slot S.

The usual opposed Wrist pin bosses 8 of relatively heavy construction are integrally formed with the inner walls of skirt 6 and, of course, are tapped and ground to act as bearings for the wrist pin. The outer peripheral wall of the bosses 8 are of substantially cylindrical shape.

My improved piston skirt expander comprises a relatively Wide leaf spring member E shaped in the general form of a U and having the legs 9 of the U diverging from the medial or central portion thereof. The medial portion of expander E is preferably the widest and legs 9 are preferably formed with longitudinal edges diverging gradually from the central portion to the leg extremities 9a. The leg extremities 9a are outturned and curved to nicely fit the external periphery of the tapped wrist pin bosses 8, as shown in Fig. 2, and they are further shaped concavely in a transverse direction to conform tothe circumferential shape of the bosses 1, thereby properly centering the expander in operative position and partially embracing the opposing bosses. The medial portion of expander E is shaped to form a pair of vertical, spaced, outwardly projecting, pressure applying flutings l adapted to engage and apply pressure against the piston skirt at opposite sides of slot S and in juxtaposition to the longitudinal reenforcing ribs 1 which help to define said slot. The central part of the medial portion of expander E is bent inwardly from the fiutings l E! to span the ribs 7 without contact with the same and to provide a suitable longitudinal recess for accommodating the rib and assisting in defining the pressure applying flutings.

In operative position my expander is applied, as shown in Figs. 1 to 3, inclusive, interposed between the bosses l and the inner Wall of the piston skirt intermediate of said bosses and applying pressure through the fiutings ID at each side of the longitudinal slot S through a considerable length of the skirt and a substantial part of the length of the slotted portion. The pressure is applied equally to the skirt portions at each side of the slot, enlarging the diameter of the piston taken transversely of the axis of the Wrist pin bosses and slightly ovaling the cross sectional shape of the piston to nicely take up for wear and prevent piston slap in used pistons and cylinders. This expansion conforms to the worn, outof-round shape of the cylinder due to lateral thrust in the crank action and connecting rod action of the engine. My improved expander may be applied to unslotted pistons to resiliently expand or distort the skirt to the desired, slightly oval shape to compensate for wear.

t will be noted that the over-all length of my expander from leg extremity to leg extremity is less than the are drawn between the points where the opposing bosses 8 emerge from. the inner wall of the skirt. Consequently, by spreading or expanding the leaf spring member E longitudinally and thereby decreasing the working width thereof, I am able to very easily and quickly slip my expander into a piston. This is facilitated by the close cooperation of a special pair of pliers P shown in dotted lines in Fig. 3. For engagement of expander E with pliers P, I provide a toolreceiving aperture 1 l in each of the legs 9 adjacent the out-turned extremities thereof. My pliers P have relatively short working ends each provided with an outwardly and laterally projecting stud 12 for engaging the apertured portions l l of the expander E and for expanding the length thereof and thereby decreasing the width to apply and remove the expanders readily from the arcuate chamber formed in the piston between the peripheral wall of the skirt and the adjacent portions of the wrist pin bosses. In applying the expander when the pressure on the pliers is released the distance between the leg extremities 9a is shortened and the working width of the expander increased, causing the pressure expanding flutings to engage the inner wall of the skirt while the concave configuration of the two leg extremities 9a cause the legs to partially embrace the wrist bosses 8 thereby centering the expander in the correct working position. In applying the expander as hereinafter described, the central or bridging part of the medial portion between the flutings l0 spans the ribs 1 of the type of piston illustrated and is slightly spaced therefrom while the pressure applying flutings l0 engage the skirt at opposite sides of the slot S and immediately adjacent the ribs 1 without contacting said ribs. The height of the leaf or band from which my expander is formed and the spacing of the fiutings causes application of equalized pressure to a relatively substantial area of the piston skirt.

It will, of course, be understood that various changes may be made in the form, details, arrangement and proportions of the several parts without departing from the scope of my invention.

What is claimed is:

1. The combination with a piston of an internal combustion engine having the usual head, a pair of opposed wrist pin bosses and an annular depending skirt of resilient, somewhat flexible material, of an expander comprising, a spring member shaped in the general form of a U and having a pair of legs diverging from the medial section of the U to their outer ends, said outer ends having means for engaging said wrist pin bosses with said member disposed transversely of said skirt, the medial section of said member having a central, substantially rigid, bridging portion disposed inwardly of the lateral sides of said medial section and leaving spaced pressure applying portions, at the sides of said section adapted to engage the inner wall of said skirt and apply pressure thereto at rather widely spaced portions thereof.

2. The combination with a piston of an internal combustion engine having the usual head, a pair of opposed wrist pin bosses and an annular depending skirt of resilient, somewhat flexible material, said skirt having a longitudinally disposed slot in at least a portion thereof, of an expander comprising, a spring element shaped in the general form of a U and having a pair of legs diverging from the medial section thereof toward their outer ends, said outer ends having means for engaging against said Wrist pin bosses with said member disposed transversely of said skirt and under tension, said medial section of said member having a pair of spaced, outwardly projecting, pressure applying portions adapted to engage the inner wall of said skirt at opposite sides of and adjacent the edges defining said longitudinal slot, said medial section having a substantially straight bridging portion c0nnect ing said pressure applying portions. I

3. The combination with a piston of an internal combustion engine having the usual head, a'pair of opposed wrist pin bosses and an annular depending skirt of resilient, somewhat flexible material, of an expander comprising, a leaf spring member of considerable width at its medial portion shaped in the general form of a U with the legs of said U diverging from the medial portion toward their outer ends, means on said outer ends for engaging against said wrist pin bosses with said member disposed transversely of said skirt under tension, said medial portion of said member having outwardly projecting, spaced flutings formed therein adapted to apply pressure to said skirt along spaced areas thereof, said medial portion having a central, substantially straight bridging part connecting said spaced flutings and disposed inwardly thereof.

i. The combination with a piston of an internal combustion engine having the usual head, a pair of opposed wrist pin bosses and an annular depending skirt of resilient, somewhat flexible material, said skirt having an enlarged T-shaped slot formed therein, the stem portion of said T-shaped slot extending longitudinally of said skirt and terminating short of the bottom of said skirt; of an expander comprising, a spring member of general U-shape form having symmetrically arranged legs diverging from the medial portion thereof toward their outer ends, means at said outer ends for engaging against said wrist pin bosses with said member disposed transversely of said skirt under tension, said member having a central substantially straight slot spanning section, and a pair of outthe medial portion of wardly projecting, spaced, pressure applying elements at the lateral sides thereof adapted to engage said skirt at opposite sides of and adjacent said longitudinal slot.

5. The combination with a piston of an internal combustion engine having the usual head, a pair of opposed wrist pin bosses and an annular depending skirt of resilient, somewhat flexible material, said skirt having a longitudinally disposed slot therethrough and having interior longitudinal reenforcing ribs at the sides of said slot, of an expander comprising, a leaf spring member shaped in the general form of a U with the legs thereof diverging from the medial portion, said legs having means for engaging against said Wrist pin bosses With said member disposed transversely of said skirt and under tension, the medial portion of said member having its central section throughout the height thereof inwardly disposed of the contiguous sections for spanning said slot and ribs in spaced relation thereto, said spanning section being substantially straight and leaving a pair of outwardly projecting flutings engaging said skirt at the sides of said ribs and adjacent thereto and applying expansive pressure to said skirt.

GLEN J. WOREL. 

